Monday, July 24, 2017

PowerShell on Linux

I've been working with Windows and VMware for a while now, and have really enjoyed learning PowerShell and PowerCLI. I've always preffered CLI tools to GUI tools. Possibly just because I'm old enough that the computers I started with didn't have Windows (or even X-Windows).

The more I use PowerShell, the more I like PowerShell, so I've decided to start managing the Linux servers I have at home with it, just for funsies.

The first step is to install PowerShell. PowerShell for Linux/Mac/Etc is v6, and still in beta at the time of this writing. I use Ubuntu Linux at home, and fortunately for my lazy self, there is a Apt Repo for PowerShell for Ubuntu 16.

These steps were blantantly ripped off from the actual Ubuntu 16.04 Installation Instructions. If you aren't comfortable adding the repository, there are also instructions for manually downloading the .deb package and installing it.

In UNIX and Linux, everything is a file. The shell (bash, zsh, etc) kind of turn all those files into strings, and make them available to STDOUT, which can be used on a pipeline to do things like command | sed | awk | wc or something. In PowerShell, everything is an object, which can be very powerful, but which can also be overwhelming as you're trying to get used to having to understand each object's model. They are rarely the same.

How many files are there in this directory?

Linux:

PS /home/tkennedy> find . -type f | wc -l
13

PowerShell:

PS /home/tkennedy> (Get-ChildItem -Force -Recurse -File).Count
13

The really interesting piece here, is that if I want to do something with those files, on the unix side I have to parse the list of files that `find` gives me back, and then process each file to, say, get it's `stat` results, or something. Then I have to further process all that data. Because everything is a string.

With PowerShell, I can assign the results of the Get-ChildItem command to a variable, $files, and it will create a System.Array containing all the objects for the files that were found.

PS /home/tkennedy> $files = Get-ChildItem -Force -Recurse -File

Now, because everything is an object, the $files object that I created is basically an array of all the file objects that Get-ChildItem was able to identify, and each of those file objects has all the properties that corresponds to that type of object.